Improvements in inlet port means for rotary elastic fluid actuated positive displacement power plants



2,845,777 LASTIC Aug. 5, 1958 H. R. NILSSON ETAL IMPROVEMENTS IN INLET PORT MEANS FOR ROTARY E FLUID ACTUATED POSITIVE DISPLACEMENT POWER PLANTS Filed May 18, 1948 2 Sheets-Sheet 1 ATTORNEY g- 5, 1958 H. R. NILSSON EI'AL 2,845,777

IMPROVEMENTS IN INLET PORT MEANS FOR ROTARY ELASTIC FLUID ACTUATED POSITIVE DISPLACEMENT POWER PLANTS Filed May 18, 1948 2 Sheets-Sheet 2 ATTORNEY ings may be in communication United States Patent IMPROVEMENTS IN INLET PORT MEANS FOR ROTARY ELASTIC FLUID ACTUATED POSI- TIVE DISPLACEMENT POWER PLANTS Hans Robert Nilsson and Teodor Immanuel Lindhagen, Stockholm, Sweden, assignors, by mesne assignments, to Svenska Rotor Maskiner Aktiebolag, N acka, Sweden, a corporation of Sweden Application May 18, 1948, Serial No. 27,767 14 Claims. (Cl. 60-39.61)

The present invention relates to so called displacement engines, the primary parts of which consist of at least two rotors, rotatably mounted in a housing and intermeshing with each other, said rotors having helical lands and grooves. More specifically the invention relates to such engines of this type which under expansion of an elastic fluid in the working or expansion chambers formed between the lands and grooves of the rotors work as motors.

For motors of this type co-operating with a feeder section producing the necessary motive fluid there has been proposed in our copending U. S. Patent No. 2,627; 162 granted February 3, 1953, an arrangement which automatically increases the output torque at decreasing speed of the power motor by building up the pressure.

The present invention contemplates a new design of displacement motors in order to make possible an increase of the output torque at decreasing motor speed, whereby said new design may be used separately or in combination with a device according to the aforesaid U. S. Patent No. 2,627,162.

The main object of this invention is to adapt the torque of the motor to the actual demand at load by rendering possible variable filling of the expansion chambers of the motors.

In order to obtain the main object as well as other objects set forth in the following description the apparatus according to the invention is substantially characterized thereby, that the displacement motors are provided with special supply openings at the inlet port for working medium, said openings being in communication with a source of compressed elastic fluid and with the expansion chambers of the motor in such a way that additional supply of motive fluid to the expansion chambers takes place through these openings even after the actual expansion chamber and the inlet port are shut ofi? from communication with each other by the rotor threads, said supply openings being shut off from communication with the working chambers of the rotors before, at the same time as, or shortly after, the expansion chamber in question exhausts to the motor outlet. Thus the supply openwith a separate source of motive fluid or with the same feeder section which supplies the motor with motive fluid. If in the last mentioned case the feeder unit consists of a compressor with driving engine and combustion chamber the connections to the supply openings can be arranged before the combustion chamber if it is desirable to feed cold compressed fluid through said openings, for instance in case they are provided with controlling valves which are to be cooled, or, alternatively, after the combustion chamber if cold fluid is not necessary.

In the following the invention will be described more in detail with reference to the accompanying drawings.

In the drawings:

Fig. 1 shows a power plant comprising a feeder unit consisting of a compressor with driving motor, a combustion chamber and a displacement motor for deliverthe inner surface of the ing useful output, said displacement motor being con-, structed in accordance with the invention.

Fig. 2 is a cross section on the line 2-2 of Fig. 1, giving a view of the inside surface of the end plate and illustrating an embodiment of the invention with the supply openings formed as excavations 'or grooves in communication with the motor inlet port.

Figs. 3 and 4 are sections on the lines -33 and 44 respectively of Fig. 2.

Fig. 5 shows a PV-diagram illustrating the working characteristic of a displacement motor, alternatively with and without supply openings.

Fig. 6 shows another design of the supply openings for a motor of the same type as the power motor as shown in Fig. 1. t

Fig. 7 shows a cross section corresponding to Fig. 6 for an embodiment provided with controlling valves in the supply openings.

The power plant according to Fig. 1 consists, as mentioned above, of a feeder unit 10 comprising a compressor 12 with driving motor 14, a combustion chamber 16 and a power motor gaseous medium, generally air, is sucked into and compressed by the compressor 14 and the likewise cooled power motor 18 on its way to the combustion chamber 16, where the air is heated by burning fuel therein to a suitable temperature and then conducted to the respective motors, where its heat content is converted to mechanical energy by expansion. The characteristic feature is that the power motor must be of the displacement type.

In order to make possible an increased filling of the compressed elastic fluid to the expansion chambers occurs.

even after they have been cut off from the main inlet port.

In the embodiment ings are formed as grooves or excavations 102 and 104 in inlet end plate of the motor housing, said grooves extending from the inlet port 106 peripherally over a portion of the circumference of each rotor. The said supply openings or grooves should be of such extension that the communication between the inlet port and the expansion chambers is maintained through the same-for such a part of the expansion period that the desired charging is obtained. In any case said extension must be restricted so that the charging is interrupted at least when the working or expansion chambers open to the motor outlet, or possibly shortly thereafter.

In previous designs the communication between the inlet port and an expansion chamber has been cut off by the rotor threads closing the expansion chamber when said threads pass the line defining the ends of the main inlet port 106. Due to the extension of the grooves 102 and 104 the expansion chamber of the motor will be in communication with the inlet port for a further period of time necessary for threads which shut off communication to move to the end points 112 and 114, respectively,

of the grooves or supply openings 102 and 104, respectively.

The quantity or volume of working medium flowing through said supply openings in relation to the increase in volume of the working chambers upon rotation of the rotors from the position 108 to 112 and from the position 110 to 114, respectively, is to be such that at normal speed the flow through said supply openings has practically no influence on themotorcharacteristics. With de- 18, deliveringthe net output. A.

12 and passes in the embodi .ment illustrated through the cooled compressor motor of a plant according to Fig. 1

shown in Fig. 2 the supply openinto the working chambers of the motor through thesupply openings will be of increasing influence resulting in full pressure prevailing in the working chambers at stall until at beginning. rotation the closingedges of the respective threads pass. the end points 112 and 114 of the grooves 102 and 104, respectively. The filling of the working chambers of the motor after the inlet port proper has been shut off will thus result in a higher average pressure in the working chambers during the expansion period and thereby in an'increased torque on the ouput shaft. By varying theextension of the grooves 102 and 104 in peripheral direction, as well as by varying the through flow area, it is obviously possible to influence'the torque-characteristic of the motor as desired.

In the embodiment showrrin Fig. 6 the supply opening's 202 by means of a' channel or the like 264 are in communication with a source of elastic fluid under pressure, for instance the pipe or duct to the inlet port 106 for the motive fluid to the motor.

Fig. 7 illustrates a similar embodiment to that shown in Fig. 6 with the difference, however, that the supply openings 202 are adjustable by means of cooled valves 214i The valves 214 are provided with a cooled valve head 208 and an inlet channel 206 for cooling medium, and valve head 208 is further provided with holes or grooves 212 for injecting cooling medium into channel 204 and may also be provided with special bores 219 for introducing cooling medium through the supply openings 202 to the working chambers of the motor. The cooling medium may flow from the interior of the valves through the holes 212 into the channel 204 to mix with the motive fluid flowing to the working chambers of the motor or may flow through the bores 210 and the openings 202 directly into the working chambers. The embodiment according to Fig. 7 illustrates a valve with a pistonlike valve head. These valves may be operated manually or in any otherdesired manner.

As already mentioned Fig. of the drawings shows PV-diagrams for a displacement motor with and without supply openings. The operating conditions of a motor without supply openings is characterized by the full-drawn'line a, and the corresponding conditions of a motor provided with supply openings at stall is characterized by the dotted line b, as is evident from the above. The working condition for a motor provided with supply openings-at low speed will be characterized by a line drawn between the two limit values a and b.

We claim:

1. An'elastic fluid operated rotary engine comprising a casing having parallel intersecting circular barrels and providing a main-inlet passage terminating in a main inlet port for motive fluid and an outlet for such fluid, a

rotor mounted in each of said barrels, each of said rotors having a plurality of helical lands and grooves, said lands and grooves intermeshing to form between them and the casing a series of working chambers successively communicating in direct and unrestricted communication with said main inlet passage through said main inlet port as the rotors revolve to receive an unrestricted flow of motive fluid directly from said main inlet passage for expansion in said chambers, said chambers being suc cessively cut ofl from direct and unrestricted communication through said main inlet port with said main inlet passage by the travel of successive lands past the perimeter of said main inlet port and further passage means restricted with respect to said main inlet port for supplying a relatively restricted flow of motive fluid to said chambers during the expansion phase of the cycle but after said direct and unrestricted communication of said chambers with said main inlet passage through said main inlet port has been cut off by said lands.

ZLAnengine as set forth in claim 1 in which said main inlet port and said means are in communication with a-common source ofmotive fluid.

3. An engine as set forth in claim 2 in which said means comprise channels formed in said casing and extending laterally from said main inlet port so as to remain in communication with said chambers after the chambers have been cut ofi from open communication with said main inlet.

4. An engine as setforth in claim 3 in which said channels have relatively small cross sectional area for limiting the rate of admission of motive fluid'to said chambers through said channels.

5. An engine as set forth in claim 4 in which the flow area through said channels is so restricted relative'to' the flow area through said main inlet port that at normal full speed operation of the rotors the quantity of motive fluid supplied tosaid chambers through said channels is insuflicient to materially alter the expansion characteristic of the bodies of motive fluid in the chambers.

6. An engine as set forth in claim 5 in which said channels extend laterally a sufiicient'distance to remain in communication with said chambers until the rotors reach positions of rotation in which the chambers are approximately at the end of the expansion phase of the cycle, whereby to enable substantially full inlet pressure to be built up in said chambers when the engine is stalled.

7. An elastic fluid operated rotary engine comprising a casing having parallel intersecting cylindrical barrels and providing a main inlet for motive fluid and an outlet for said fluid, a rotor mounted in each of said'barrels, each of said rotors having a plurality of helical lands and grooves, said lands and grooves intermeshing to form between them and the casing a series of Working chambers successively communicating with said main inlet as the rotors revolve to receive motive fluid for expansion in said chambers, said chambers being successively cut off from communication with said main inlet by the passage of successive lands past said main inlet, and auxiliary inlet ports in said casing laterally spaced from said main inlet for supplying additional motive fluid to said chambers during the expansion phase of the cycle but after communication with said main'inlet has been cut off by said lands.

8. An engine as set forth in claim 7 in which said main inlet port and said auxiliary inlet ports are in communication With different sources of motive fluid.

9. An engine as set forth in claim 8 in which said main inlet port is in communication with a source of motive fluid of higher temperature than that from the source supplying said auxiliary inlet ports.

10. An engine as set forth in claim 7 in which valves are provided for controlling said auxiliary inlet ports.

11. An engine as set forth in claim 10 including means for admitting elastic pressure fluid to said valves to cool the same.

12. An engine as set forth in claim 11 including means for discharging the cooling fluid to said chambers through said auxiliary inlet ports.

13. Power plant apparatus including an elastic fluid operated rotary engine, said engine comprising a casing having parallel intersecting cylindrical barrels and providing a main inlet for motive fluid and an outlet for said fluid, a rotor mounted in each of said barrels, each of said rotors having a plurality of helical lands and grooves, said lands and grooves intermeshing to form between them and the casing a series of working chambers successively communicating with said main inlet as the rotors revolve to receive motive fluid for expansion in said chambers, said chambers being successively cut off from communicationwith' said main inlet by the passage of successive lands past said main inlet and separate auxiliary inlet ports in said casing for supplying additional motive fluid to said chambers during the expansion phase of the cycle-but after communication with said main inlet has'beencut otf by said lands and a source of motive fluid for said engine comprising compressormeans for compressing the fluid and heating means for heatingrthe compressed fluid References Cited in the file of this patent UNITED STATES PATENTS 724,907 Matteson Apr. 7, 1903 6 McCune et a1. Sept. 7, 1909 Davies Dec. 4, 1928 Lysholm June 3, 1941 Miksits July 8, 1941 Hermitte Mar. 20, 1945 Youngash Mar. 5, 1946 Paget Aug. 5, 1947 Paget Oct. 18, 1949 Boestad et a1 Nov. 8, 1949 Sdille Dec. 16, 1952 FOREIGN PATENTS Great Britain Sept. 3, 1895 Great Britain Apr. 16, 1937 

